Diabetic autonomic neuropathy (DAN) is a serious complication of diabetes and carries up to a five-fold increased risk of mortality. This high mortality rate is related in large part to silent myocardial ischemia, cardiac arrhythmias, and cardio-respiratory instability. Despite its relationship to an increased risk of cardiovascular mortality and its association with significant morbidity, the importance of DAN is not fully appreciated and it frequently goes undiagnosed. A major reason for this is that whilst severe symptomatic DAN is relatively uncommon, many people have sub-clinical or asymptomatic DAN. Early detection of this disorder might lead to a better prognosis for people with diabetes, by the deployment of interventions which will slow or possibly even reverse its progression. However, unlike other microvascular complications, there is currently no simple test or biomarker that would allow for screening large numbers of people. It has also limited the study of the natural history of the disorder and the impact of interventions in large-scale prospective trials. Dynamic pupillography and spectral analysis of heart rate variability are safe, noninvasive, quick and easy techniques that may allow for more widespread assessment and earlier detection of autonomic dysfunction both in the research and clinical setting. They result in a variety of different measures that may act as novel biomarkers for different types and stages of autonomic neuropathy. The aim of this cross-sectional study is to assess the usefulness of these different techniques by comparing them with standard cardiovascular reflex tests for the assessment of autonomic neuropathy. It will comprise of 5 groups (n=20 in each) consisting of: people with diabetes and (1) symptomatic autonomic neuropathy; (2) asymptomatic autonomic neuropathy; (3) sub-clinical autonomic neuropathy; (4) no autonomic neuropathy and (5) healthy volunteers. Also, analysis of the results will provide the range of variation for the analysed parameters among the different groups of subjects studied and allow for refinement and standardisation of these techniques. [unreadable] [unreadable] [unreadable]